Devices with critical dimensions on the order of 90 nanometers have involved integration of copper conductors and low-k dielectrics. Devices with critical dimensions on the order of 90 nanometers require alternating material deposition processes and planarization processes. Following almost each step in the fabrication process, e.g., a planarization step, a trenching step, or an etching step, cleaning processes are required to remove residues of the plasma etch, oxidizer, abrasive, metal or other liquids or particles remaining which contaminate the surface of the wafer. Prior art devices were fabricated from aluminum and/or tungsten conductors with silica dielectrics. Fabrication of the current advanced generation of devices require copper conductors and low-k dielectric materials (typically carbon-silica or porous silica materials), both of which can react with and be damaged by various classes of prior art cleaners.
Low-k dielectrics in particular may be damaged in the cleaning process as evidenced by etching, changes in porosity/size, and ultimately changes in dielectric properties. Time required to remove residues depends on the nature of the residue, the process (heating, crosslinking, etching, baking, and/or ashing) by which it is created, and whether batch or single wafer cleaning processes are used. Some residues may be cleaned in a very short period of time, while some residues require much longer cleaning processes. Compatibility with both the low-k dielectric and with the conductor over the duration of contact with the cleaner is a desired characteristic.
Cleaning processes fall into two broad process classes: batch and single wafer. Batch cleaning typically involves multiple wafers, and the cleaning process occurs on the order of minutes, usually by contacting the wafers with an agitated cleaning solution at a temperature between about 20° C. and about 100° C., typically between 30° C. and 75° C., for a period of time ranging from 3 minutes to about 60 minutes, typically between 10 to 30 minutes. In a batch mode, the plurality of wafers are typically immersed in the cleaning solution or exposed to a constant spray of cleaning solution. The single wafer cleaning process involves cleaning under more rigid conditions of agitation and contact, at temperatures similar to or up to about 20° C. higher than comparable immersion process temperatures, but for a period of time that ranges from about 5 seconds but less than 3 minutes, and typically between 30 to 90 seconds, as the composition is dispensed onto a spinning wafer.
Semi-aqueous cleaners comprising a fluorine-containing component, solvent, and water are known.
1) Japanese patent laying open no. 2003-122028, to Kenji et al., describes a composition comprising 0.5% to 10% of a fluorine compound, greater than 30% of a mixed amide/ether solvent and water, and teaches that at solvent concentrations less than 30% corrosion of the wiring material becomes intense.
2) Japanese patent laying open no. 2001-5200, to Yoko et al., describes a resist removing composition for substrates comprising aluminum wiring, the composition comprising 0.1% to 2% ammonium fluoride, 20% to 98.8% of a polar organic solvent, 0.05% to 1.9% ascorbic acid, and 1% to 79.8% water, with pH less than 5.0. The listed polar organic solvents are N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, ethylene glycol, and propylene glycol.
3) U.S. Pat. No.5,792,274, to Tanabe et al., describes a remover solution composition for resist which comprises (a) 0.2% to 8% a salt of hydrofluoric acid with a metal-free base, (b) 30% to 90% of a water-soluble organic solvent such as a glycol ether, and (c) water and optionally (d) an anticorrosive, at a pH of 5 to 8.
4) U.S. Pat. No.5,939,336 describes residue remover compositions of ammonium fluoride, propylene glycol, ammonia and water, at a pH of from 7 to 8.
5) U.S. Pat. No.5,972,862 describes a post-etch residue remover having: (A) 0.1% to 15% of a fluoride-containing compound such as hydrofluoric acid or ammonium fluoride; (B) 1% to 80% of a polar organic solvent selected from a list including amides, lactones, alcohols, alkyl acetates, alkyl lactates, alkylene glycols, glycol ethers, and sulfoxides; (C) 0.01% to 5% of an phosphoric acid, phosphorous acid, hypophosphorous acid, polyphosphoric acid, or an organic acid; and (D) 1% to 50% of a quaternary ammonium salt. Water is not a specified component of the remover, and while there is no range specified for water, one example was described as containing 45.9% water. Examples have 1-10% NH4F, 0.1-1% organic acid, and 35-69% amide solvent, and presumably a balance (˜30% to ˜60%) water.
6) U.S. Pat. No.5,792,274 describes a resist/residue remover having 0.2% to 8% of a salt of metal-free base and HF, 30% to 90% of a water-soluble organic solvent, and water where the pH is 5-8. The preferred solvent is ethylene glycol or ethylene glycol and dimethylsulfoxide.
7) U.S. Pat. No.6,235,693 describes residues removers comprising 0.01% to 10% of fluoride compounds, 20% to 50% water, 20% to 80% of a piperidone and from 0 to 50% of an organic sulfoxide or glycol solvent, said composition having a pH between about 6 and about 10.
8) U.S. Pat. No.6,468,951 describes a composition to remove silica residue from a borophosphosilicate semiconductor wafer, said composition having a basic or an acidic pH, and being comprised of: water; 0.01% to 95% of a hydroxyl-functional solvent such as ethylene glycol or an alcohol; aqueous hydrofluoric acid; a tetraalkyylammonium hydroxide; and about 0.001 wt % to about 10 wt % of a surfactant. The patent does not mention use of the composition with copper-containing substrates.
9) U.S. Pat. No.6,638,899 describes a photoresist remover comprising hydrofluoric acid, a base free from metal ions, 30% to 80% of a water-soluble organic, water, and an alkali, wherein the pH of the remover is 8.5 to 10.
10) JP 3255551 describes a composition having 0.5-40% HF, 40-99.5% water, water-soluble organic solvent, and 0.5-40% anticorrosion agent, useful for removing resist in short time at low temperatures.
11) Finally, U.S. published Application No. 2004/0106531, the disclosure of which is incorporated herein by reference thereto specifically for the semiconductor fabrication processes which form various types residue, each type of which can be removed with compositions of the present invention. This application discloses removers useful for copper/low-k material substrates, the removers comprising a metal-free salt of hydrogen fluoride; 50% to 98% of a water-soluble organic solvent; an acid; and water.
With the continuing reduction in device critical dimensions and continuing needs for production efficiency and device performance, there is a need for fluorine-containing cleaning compositions with low solvent content which are effective in both batch and single wafer processes.